U.S. Pat. No. 4,409,506 (Ito), which is incorporated by reference herein in its entirety, allegedly recites that “[w]hen an induction motor is speed-controlled with a variable frequency power supply including thyristor inverters, operating loss due to harmonics components is increased in a rotor of the induction motor. In order to diverge additional operating loss into an appreciable depth of the rotor to thereby suppress the increase in the operating loss, the rotor comprises a cylindrical member having a circumferential resistivity which is larger than axial and radial resistivities and circumferential permeability which is smaller than axial and radial permeabilities, and a core disposed in the cylindrical member and having an axial permeability which is smaller than circumferential and radial permeabilities.” See Abstract.
U.S. Pat. No. 4,751,417 (Krinickas), which is incorporated by reference herein in its entirety, allegedly recites that “[i]n order to improve the efficiency of electric machines, by reducing losses caused by eddy currents induced by high frequency fluxes, the outer surface of the rotor, including the rotor pole face, has a plurality of circumferential grooves. The grooves are provided in axially spaced relation along the rotor. Preferably, the method of reducing losses includes the step of forming the grooves by laser cutting, which permits the width and spacing of the grooves to be minimized so as to maximize loss reduction by increasing resistance to eddy currents.” See Abstract.
U.S. Pat. No. 5,861,700 (Kim), which is incorporated by reference herein in its entirety, allegedly recites a “rotor for an induction motor includes a core having a central hole extending axially therethrough for receiving a shaft. A plurality of large spaces are formed in the core radially outside of the center hole. The spaces are filled with a non-ferrous metal, and blowholes extend through the non-ferrous metal for conducting cooling air through the core.” See Abstract.
U.S. Pat. No. 6,483,210 (Soderberg), which is incorporated by reference herein in its entirety, allegedly recites that “[t]he invention relates to a method of improving the performance of a rotary electric machine through improved cooling, whereby a cooling fluid is conducted through axial cooling channels (15) in the rotor, radially inwardly of the rotor winding grooves (14), whereby the cooling fluid being mainly active in cooling the machine is conducted through axial cooling channels (15), or alternatively groups of cooling channels, that are provided essentially symmetrically with reference to the magnetic flow paths in the rotor, for achieving a symmetry in the magnetic circuit and thereby good electrical properties for the machine. The invention is also directed to a rotary electric machine, a rotor therefor and a use thereof.” See Abstract.